360 Lose timing belt.

Had the same "issue" when I opened the cover for the first time... A little "panic moment" but happy nothing got broken...

Well, it turns out that it all depends where and how the motor stopped the last time it was run. You cannot check the tension of the belt at anywhere else than TDC on the compression stroke of Cyl #1. So turn the engine by hand clockwise using a 36 or 32mm (don't recall) on the main crankshaft pulley until you bring the engine to TDC and check the tension then.

Now, it looks like you've already loosen the tensioner bearing so unfortunately you'll have to re-do the tension at TDC following the workshop manual procedure. PM me if you need a link to download it.

 

Can you explain why? Are you saying that the cam belt tension changes according to the position of the crankshaft? How does it do that?

 

It's all due to where the cams stop in their cycle.
Depending on the stop position, the valve springs create a torque on each cam in one direction or the other. That results in variable tensions in the 3 strands of the belt.
Belt tension must always be checked at the same position and Ferrari selected the #1 TDC.

 

My old mondial, you could check the tension by finding the longest run and when you could twist it by 45 deg in the middle of the long run , then it was right. Lot to be said for the simple old engines

 

Check your PM...

 

Hmmm. I could see that if there was only one set of cam lobes involved but with cam lobes pointing every which way down the length of the camshafts it doesn't seem to make sense to me. But, if it says that is the WSM then it must be so!

 

On our V8, the cam lobes are 90° apart on each camshaft. If you try to turn such a camshaft by hand (no belt), you will find that it can stay fix (no torque due to valve springs) only at some stable and unstable positions. Stable positions are where 2 cam lobes are compensating each other, unstable is when 1 cam lobe is at max opening with almost no effect of other cams.
In between these stable positions (where the camshaft has no effect on belt tension) the torque resulting of all the valve springs and cam lobes can be in one direction or the other. If the engine stop there (between stable positions) this torque will have a direct impact on the tension of the 2 strands of the belt connected to the pulley.

 

I totally agree with eric355. I can say from experience if a particular lifter is on the high portion of the slope of a cam lobe it is pre-loaded by the valve spring, and can cause the cam to rotate. In This case would be toward the leading edge of the cam pulley because it can cause slack on that portion of the belt that is normally tight when engine is spinning forward. That would be sort of the equivalent of spinning the motor backwards even if the crank didn’t move.

Cam rotation happened to me when I was degreeing my engine. Had the cam pulley bolts loose and cam slipped due to that preload from the valve spring on a cam lobe. My Heart skipped a beat when cam slipped.


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